Electric hair dryers are designed to produce a stream of air which is heated by an electrical element and is delivered by action of a fan. The very design of the hair dryer, in particular its cylindrical circular-section geometry which must house the fan, gives the stream of air a circular cross section. In certain cases, however, users want a relatively broad flat lamina of air.
To accomplish a laminar flow, it is usual practice to fit a nozzle on the outlet end of the hair dryer where the stream of air is produced. The nozzle ends in a flattened outlet generally in the form of an elongate rectangle. A nozzle of this kind can be fitted permanently to the outlet opening of the hair dryer, but it is usually detachable. In the case of a detachable nozzle, the user may mislay it, and thus, experiences the nuisance of looking after an extra component.
While the hair dryer is in use, the circular stream and the broad flat stream are sometimes found to be alternately necessary and thus oblige the user to remove and replace the nozzle. This quickly becomes a nuisance, especially as it is hot.
The prior art includes a number of teachings regarding various air flow configurations from hair dryers. French Patent 2 640 857 to Bomtoux illustrates a nozzle arrangement which is configured from a flexible material. Rotation of the nozzle causes a mechanism to alter the nozzle's cylindrical opening to a rectangular configuration so as to create a laminar air flow.
U.S. Pat. No. 5,467,540 to Bastien describes an air diffuser that is mountable on the exhaust end of a hair dryer. Within the barrel of the diffuser is a perforated valve plate which can be rotated to partially block air flow. Under such circumstances, heated air exits through the valve plate perforations and through perforations that are present about the circumference of the barrel.
U.S. Pat. Nos. 5,598,640 and 5,661,910 to Schepisi describe a hair dryer having a diffuser mounted on its exhaust end. A pair of flapper valve plates in the diffuser can be actuated to either block the principle air opening or to open it. The barrel includes a plurality of holes which act as exhaust holes when the principal air exhaust path is closed by the flapper valves. Air exhaust through the barrel is controlled by the positioning of a cylinder that is slidably mounted thereon. By moving the cylinder, the flapper valves are actuated and holes in the cylinder line-up with holes in the barrel of the hair dryer.
U.S. Pat. No. 5,157,757 to McDougall describes a hand-held hair dryer which includes a rotatable valve that blocks, in one position, air flow through a central exhaust path and redirects the air flow through openings in the barrel.
U.S. Pat. No. 5,054,211 to Shulman describes a hair dryer attachment that includes an air deflection plate that is rotatable about an axis that is coextensive with the axis of the air exhaust path of the hair dryer. U.S. Pat. No. 4,525,623; to DaSilva describes a hair dryer with an air outlet that includes a pair of valve members that are pivotally mounted. The positioning of the valve members is controlled by a knob that extends through the dryer housing.
U.S. Pat. No. 5,842,286 to Cantor describes a hair dryer having a barrel with a plurality of holes positioned about its periphery. Separate chambers are provided within the barrel to direct hot air, both to a principal exit and to the holes that are positioned along the barrel.